Your enlarger is fine. An expensive one won't give you better prints, and even though that's a low end lens, the results look plenty sharp enough to me! Never having printed on graded papers I have no suggestions on that, but the prints look very good indeed. Not too contrasty to my eyes.
Test strips are how you dial in the image. It does take a little time, but beats printing an image only to find out that the exposure/filtering is off. I don't use a timer anymore either and just count the seconds. It's accurate enough for my negs. And speaking of negs, the huge difference in exposure times you're experiencing is how it it goes w/ negs that weren't exposed perfectly.
You should buy an inexpensive filter set and learn how to use them to solve printing issues. It all takes time, and for a second printing session you should be proud of what you did, even if you see room for improvement. I hate to sound old fashioned, but this is all about practice, practice, practice. Finding a neighborhood college that still has a darkroom is a good idea too. Whatever you paid for the class and materials would be less hassle and less money than burning thru printing paper w/o a little guidance.